1. Field of the Invention
The invention relates to the positioning of glass sheets which are passing flat on a conveyer, with a view toward curving them.
2. Background of the Prior Art
In order to be able to provide correctly curved sheets of glass, it is first important for said sheets of glass to be correctly positioned in relation to the curving equipment. This is general and relates to all curving techniques, but must particularly be respected when the curving technique is used in accordance with the method in which the sheets of glass are supplied against an upper component, which is gnerally shaped, whose profile they adopt, in order to be subsequently released, possibly onto a complementary lower curving component arranged beneath the upper component, on which the shaping of the sheets of glass is carried out or is continued.
In order for the curvature taken by the sheets of glass to be correct, it is important to position them in a precise manner in relation to the upper component and possibly also in relation to the complementary lower curving component.
In addition, in order to increase manufacturing capabilities, several sheets of glass need to be treated simultaneously and, in that case, it is important not only to correctly position the sheets of glass in relation to the curving equipment, but also in relation to each other.
It is known to correctly orient sheets of glass prior to their being placed into a reheating furnace to curve them, for example by manual action or by guiding their lateral edge with a guide bar which is correctly oriented and is arranged along the furnace conveyer.
It is also known to use optical means for detection of the front edge of the sheets of glass combined with the movement of the conveyer, which can therefore cause the stoppage of the sheets of glass when they arrive under the possibly shaped upper component or components against which they will be subsequently applied.
However, these positioning means are insufficient and inexact. In effect, during its transport along the reheating furnace, a sheet of glass slides to some degree on the conveyer belt and the adjustment of position which is made at the entry is no longer necessarily appropriate on arrival under the curving equipment.
Moreover the adjustments in position made on the cold glass do not always remain valid on hot glass which could have become deformed.
In addition, stopping the glass with electronically relayed optical detectors in hot atmospheres is not sufficiently precise and does not in all cases provide accuracy on the order of that which is presently required, i.e., on the order of 1/10 mm.